挤压温度对固溶态Mg-2.0Zn-0.5Zr-3.0Gd合金微观组织及耐腐蚀性能的影响

利用金相显微镜、扫描电镜及透射电镜等测试手段研究了挤压温度对固溶态Mg-2.0Zn-0.5Zr-3.0Gd镁合金显微组织的影响。同时,采用浸泡实验和电化学测试等方法研究了合金在模拟体液中的腐蚀行为。结果表明：挤压态合金主要由大的变形晶粒和动态再结晶晶粒组成,析出相由纳米级的棒状(Mg, Zn)₃Gd相和颗粒状的Mg₂Zn₁₁相组成。挤压温度在340～360 ℃时,合金中动态再结晶晶粒的体积分数随着挤压温度的升高而增加,腐蚀速率随着挤压温度的升高而降低。当挤压温度为360 ℃时,合金发了完全动态再结晶,具有较好的耐腐蚀性,静态腐蚀速率为0.527 mm/y,腐蚀形式为均匀腐蚀。当温度升高至380 ℃时,部分动态再结晶晶粒发生异常长大现象,导致腐蚀速率随着挤压温度的升高而升高。     

Mg-0.5Zr-1.8Zn-xGd生物镁合金的组织与性能

在较高的熔炼温度(780±5 ℃)下,研究了Gd含量对铸态Mg-0.5Zr-1.8Zn-xGd生物镁合金组织、力学性能及耐腐蚀性能的影响。结果表明：Gd含量在0-2.5wt%时,合金的晶粒尺寸随Gd含量的增加逐渐减小,未含Gd合金主要由α-Mg和少量分散的微米级Zr颗粒组成,而含Gd合金则主要由α-Mg和不同形貌的(Mg, Zn)₃Gd相组成。合金的力学性能随Gd含量的增加先升高后降低,Gd含量为1.5wt%时,合金具有较好的力学性能。与此同时,合金的耐腐蚀性能也随Gd含量的增加先增强后减弱,Gd含量为1.5wt%时,分布均匀且尺寸细小的网状第二相使其具有较好的耐腐蚀性能,在120 h的浸泡实验中,静态腐蚀速率为0.801±0.04 mm/a,腐蚀形貌较为均匀。     

挤压温度对Mg-2.0Zn-0.5Zr-3.0Gd生物降解镁合金组织、力学性能及耐腐蚀性能的影响

研究挤压温度对铸态Mg-2.0Zn-0.5Zr-3.0Gd生物镁合金组织、力学性能及耐腐蚀性能的影响。结果表明:挤压温度在330～350℃时,动态再结晶的体积分数随挤压温度的升高而增加;在350～370℃时,动态再结晶的体积分数随温度的升高而降低。挤压态合金的析出相主要由纳米级的棒状(Mg, Zn)_3Gd相和新析出的颗粒状Mg_2Zn_(11)相组成。合金的力学性能与动态再结晶晶粒的体积分数成正比关系。挤压温度为350℃时,合金的抗拉强度、屈服强度及伸长率分别为(247±3) MPa、(214±3) MPa和(26.7±1.1)%。随着挤压温度的升高,合金的腐蚀速率先减小后增大,挤压温度为350℃时,合金的静态腐蚀速率及析氢腐蚀速率分别为0.614 mm/a和0.598 mm/a。     

固溶处理对Mg-2.0Zn-0.5Zr-3.0Gd生物降解镁合金组织及耐腐蚀性能的影响

采用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)研究固溶处理温度对Mg-2.0Zn-0.5Zr-3.0Gd(质量分数,%)生物镁合金显微组织的影响,通过失重、析氢和电化学方法研究合金在模拟体液(SBF)中的耐腐蚀性能。结果表明:铸态合金中,第二相(Mg,Zn)3Gd在合金基体中呈网状分布。固溶处理温度在460～500℃时,合金的晶粒尺寸随温度的升高而逐渐增大,温度为480℃时,没有溶入基体的(Mg,Zn)3Gd相以颗粒状或长条状的形式存在于基体中,部分颗粒与α-Mg基体具有共格关系。随着固溶处理温度的升高,合金的腐蚀速率先减小后增大,固溶处理温度在480℃时,合金的耐腐蚀性能比铸态合金的有了较大的提高。在120 h的浸泡实验中,合金的腐蚀速率在最后24 h时逐渐趋于稳定。     

Gd含量对挤压态Mg-0.5Zr-1.8Zn-xGd生物镁合金组织及耐腐蚀性能的影响EI北大核心CSCD

研究了Gd含量对挤压态Mg-0.5Zr-1.8Zn-x Gd(0~2.5%,质量分数)生物镁合金组织及耐腐蚀性能的影响。结果表明:挤压比为7.7、挤压温度为350℃时,合金发生了完全动态再结晶,其晶粒尺寸随Gd含量的增加先减小,最后趋于稳定。合金中的第二相主要由颗粒状(Mg, Zn)_(3)Gd相和Mg_(2)Zn_(11)相组成,其数量、尺寸及体积分数随Gd含量的增加逐渐增大,同时,纳米级棒状(Mg, Zn)_(3)Gd相与合金基体具有半共格界面关系。Gd含量大于2.0%(质量分数)时,部分未溶第二相以弯曲线条状在合金基体中随机分布,其尺寸及数量随Gd含量的增加逐渐增大。合金的耐腐蚀性能随Gd含量的增加先增强后减弱,Gd含量为1.0%(质量分数)时,合金具有较好的耐腐蚀性能。     

Al含量对Mg-2.0Zn-0.4Mn合金组织、力学性能及耐腐蚀性能的影响

采用X射线衍射仪、光学显微镜、扫描电镜和透射电镜等研究了铸态Mg-2.0Zn-0.4Mn-xAl (x=0, 2.0, 3.0, 4.0, 5.0, 6.0 mass%)合金的物相和显微组织,采用拉伸实验测试了合金的力学性能,采用静态质量损失法和电化学测试实验研究了合金的耐腐蚀性能。结果表明：含Al合金的组织主要由α-Mg基体及不同形貌的Mg₂(Zn, Al)₁₁和MgZn₂第二相组成。随着Al含量的增加,合金的晶粒尺寸逐渐减小,其力学性能和耐腐蚀性能先升高后降低。当Al含量为4.0 mass%时,合金具有较好的力学性能及耐腐蚀性能,其极限抗拉强度、屈服强度及伸长率分别为(158.4±4.2) MPa、(119.2±5.8) MPa及(15.6±0.5)%,在3.5%NaCl溶液中浸泡72 h后,其平均静态腐蚀速率和析氢腐蚀速率分别为(0.958±0.057)和(0.933±0.051) mm/y。     

挤压温度对Mg-2.0Zn-0.3Zr-0.9Y新型镁合金组织和性能的影响

研究了不同挤压温度对Mg-2.0Zn-0.3Zr-0.9Y新型镁合金组织和性能的影响。结果表明,降低挤压温度,Mg-2.0Zn-0.3Zr-0.9Y合金的平均晶粒尺寸得到显著细化,合金的屈服强度和抗拉强度得到大幅提高,而延伸率变化不大。随着挤压温度的降低,{10ī2}织构强度不断增强,{0002}基面环形织构强度减弱。Mg-2.0Zn-0.3Zr-0.9Y合金的力学性能不但受到组织平均晶粒大小的影响,还受到织构分布的影响。挤压温度为330℃时可获得细小的组织和优良的力学性能,平均晶粒尺寸达到1.76μm,合金抗拉强度达到323MPa,屈服强度为309MPa,延伸率为21.92%。     

固溶温度对车用Mg-8.5Gd-5.5Zn-2.0Zr-0.2Y镁合金组织和耐腐蚀性的影响

设计了Gd含量很低的车用Mg-8.5Gd-5.5Zn-2.0Zr-0.2Y镁合金,并对其腐蚀性能进行了测试,研究了固溶温度对合金组织和耐腐蚀性的影响.结果表明:固溶温度高于350℃,会降低第二相组织的热稳定性,抑制晶粒长大的钉扎作用开始降低,引起晶粒尺寸增大.经过固溶处理后的镁合金力学性能均高于铸态的力学性能;当固溶温...     

微量CaO对Mg-2Zn-0.5Sr镁合金显微组织、力学性能及腐蚀性能的影响

本文主要研究了添加0.1 wt.% CaO和0.3 wt.% CaO对Mg-2Zn-0.5Sr显微组织、力学性能及腐蚀性能的影响。光学显微镜(OM)、X射线衍射仪(XRD)及电子探针显微分析仪(EPMA)分析了材料均匀化热处理后的显微组织和第二相的组成与分布,发现CaO颗粒的加入使Mg-2Zn-0.5Sr的晶粒尺寸明显细化,而且CaO颗粒机械地富集于晶界及晶粒内的第二相与基体之间。室温拉伸试验研究材料机械性能,CaO颗粒的加入可以提高材料强度,但添加0.1 wt.% CaO时材料的塑性降低,而添加0.3 wt.% CaO时材料的塑性也有所提高,延伸率达到10.9 ± 1.1%。Kokubo模拟体液中的动电位极化曲线表明添加CaO颗粒使腐蚀电位正移。浸泡失重实验表明Mg-2Zn-0.5Sr的平均腐蚀速率为7.55 mm/year,添加0.1 wt.% CaO时腐蚀速率降低大约18.3%,添加0.3 wt.% CaO时腐蚀速率增高大约52%。CaO颗粒对显微组织及机械性能的影响决定于晶粒细化和CaO颗粒在第二相与基体之间机械富集的综合影响,而其对生物腐蚀行为的影响主要决定于晶粒细化及CaO颗粒在溶液中反应对致密稳定CaHPO4保护膜生成的促进作用。Mg-2Zn-0.5Sr/0.1CaO表现出较高的强度和较佳的耐腐蚀性能,是生物医用材料中的一种较好选择。     

Effect of high pressure on microstructure of cast Mg-8Zn-0.5Zr-0.5Gd alloy

Mg-8Zn-0.5Zr-0.5Gd alloy was prepared by high pressure solidification. Effect of high pressure on microstructure, micro-hardness and corrosion behavior in Hank's solution of the Mg-8Zn-0.5Zr-0.5Gd alloy were investigated by means of optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), and X-ray diffractometer(XRD). The results showed that, compared with the conventional solidification, high pressure solidification obviously refined the grain size of Mg-8Zn-0.5Zr-0.5Gd alloy. The grain size was refined from 200-300 μm to 100-200 μm and the secondary dendrite arm spacing reduced from 30-50 μm to 10-30 μm. Moreover, the solubility of Zn in the alloy increased and the amount and size of Mg-Zn-Gd phases significantly decreased. The micro-hardness of the alloy solidified under high pressure was improved significantly from 56.17 HV to 63.14 HV. The polarization resistance(Rp) of the alloy had a substantial increase in simulated body fl uid, thus the corrosion rate was significantly reduced from 4.0 to 2.7 mm·year-1.     

Effects of heat treatment on microstructure evolution and mechanical properties of Mg-6Zn-1.4Y-0.6Zr alloy

To investigate the effects of solution temperature and the decomposition of I-phase on the microstructure, phase composition and mechanical properties of as-cast Mg-6Zn-1.4Y-0.6Zr alloy, solution treatment at 440 oC, 460 oC and 480 oC and further aging treatment were conducted on the alloy. The results indicate that the net-like intermetallic compounds(mainly I-phase) dissolve into the α-Mg matrix gradually with the increase of solution temperature from 440 oC to 480 oC. Besides, the I-phase decomposes completely at 480 oC, with the formation of fine W-phase(thermal stable phase) and Mg_7Zn_3 phase. In addition, a great number of fine and dispersive Mg-Zn binary phases precipitate in the α-Mg matrix during the aging treatment. Due to the increase of solute atoms and the precipitation of strengthening phases, such as W-phase and Mg-Zn phases, the optimal strength is obtained after solution treatment at 460 oC for 8 h and aged at 200 oC for 16 h. The yield strength(YS), ultimate tensile strength(UTS) and elongation are 208 MPa, 257 MPa and 3.8%, respectively. Compared with the as-cast alloy, the increments of YS and UTS are 117% and 58%, respectively, while the decrement of elongation is 46%.     

Effects of erbium on microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy

Mg-7Zn-3Al-xEr(x=0.1,0.4,0.7) magnesium alloys were prepared by permanent mould casting.The effects of rare earth element of erbium on the microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy at both room temperature and elevated temperatures were investigated with optical microscopy,scanning electron microscopy/energy dispersive X-ray spectroscopy,differential scanning calorimetry,and tensile testing.The results show that the quasi-continuous grain boundary networkedτ(Mg_(32)(Al,Zn)_(49)...     

热处理工艺对Mg-6Zn-2.5Cu镁合金显微组织和力学性能的影响

利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)和力学试验机等研究了铸造Mg-6Zn-2.5Cu合金在铸态、固溶和时效处理下的显微组织和力学性能。结果表明:合金的铸态组织主要由α-Mg和(α-Mg+MgZn2+Mg2Cu+CuZnMg)共晶相组成。在455℃固溶12~36 h时,随着时间增加,固溶效果逐渐增强,且在20 h时合金获得了较理想的显微组织及218 MPa的抗拉强度和8.68%的伸长率。随后在180℃时效6~72 h后,合金的拉伸性能随时效时间的增加呈先增加后减小的趋势,其中时效24 h时后,合金的抗拉强度和硬度达到峰值,分别为249.5 MPa和64.6 HV0.1,比铸态的分别提高了66.5 MPa和26.29%,伸长率在时效12 h时后达到了峰值6.72%。铸态合金的断裂方式以沿晶断裂为主,时效处理后合金的断裂方式为准解理断裂。     

Ca对镁合金组织、力学性能和腐蚀性能的影响

研究了Ca对AZ91D镁合金显微组织、力学性能和腐蚀性能的影响.当AZ91D中加人的Ca含量大于1.0%时,β相(Mg17Al12)减少,并且在晶界上形成了网状分布的Al2Ca相.拉伸测试表明,当加入Ca含量小于1%时,可以提高合金的常温抗拉强度和延伸率,继续增大Ca含量时合金的力学性能明显下降.当AZ91D中加入的Ca含量达到1.0%时,常温抗拉强度和延伸率较AZ91D分别提高了8.2%和29.3%,并且腐蚀速率下降为AZ91D的17.2%.其原因主要是由于形成了网状分布的Al2Ca相,使镁合金的自腐蚀电位升高,腐蚀电流密度降低,从而阻碍了镁合金的腐蚀.     

Effects of Ce addition on microstructure,mechanical properties and corrosion resistance of as-cast AZ80 magnesium alloy

In this study, Ce was introduced into the AZ80 alloy and the effects of Ce addition on the microstructure, mechanical properties and corrosion resistance of the as-cast AZ80 magnesium alloy were investigated. The results show that the addition of Ce into the AZ80 alloy can not only refine the microstructure, but also result in the formation of the needle-like Al4Ce phase. These tiny Al4Ce phases are homogeneously distributed at grain boundaries and within grains. An appropriate Ce addition can also change the β-Mg17Al12 phase at the grain boundaries from continuous network to small island-like. At the same time, with the increase of Ce content from 0 to 2.0wt.%, the macro-hardness of the as-cast alloy is enhanced linearly, while impact toughness, tensile strength and elongation all firstly increase and then decrease. The AZ80 alloy containing 1.0wt.% Ce exhibits the optimal properties. Its macro-hardness, impact toughness, tensile strength and elongation are 61.90 HB, 15.50 J·cm^-2, 171.80 MPa and 3.35%, increase by 9.95%, 63%, 13.3% and 36.7%, respectively compared with the base alloy. In addition, Ce can enhance the corrosion resistance of the AZ80 magnesium alloy.     

Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

The effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy was investigated. The results indicate that adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can effectively refine the as-cast microstructure of the alloy, and the CaMgSn phase with high thermal stability is formed in the alloy. In addition, adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can also improve the creep properties of the alloy. After adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy, the second creep rate of the alloy at 150°C and 50 MPa for 100 h decreases from 4.67 × 10⁻⁸ to 1.43 × 10⁻⁸ s⁻¹. The strengthening mechanism is mainly attributed to the microstructural refinement and the formation of CaMgSn phase.